Recently, the packing density of hard disk drives (HDDs), which are a magnetic recorder and reproducing devices, has improved considerably, and now even the packing density of mass-produced HDDs has reached 80 Gbpsi (gigabits per square inch). Thus, even small HDDs have high capacity. For example, 80 Gbpsi can realizes a capacity of 6 GB for a 1-inch HDD.
Realizing high recording capacity for a small size of about 1 inch makes wide application to mobile applications such as mobile phones, mobile music players, and personal digital assistances (PDAs) possible. Already mobile music players on which a 1-inch HDD is mounted are being sold, and certain new markets have been developed.
For a magnetic recording medium for hard disk drives, a structure in which that metal films are laminated on a substrate for a magnetic recording medium by a sputtering method commonly known. Aluminum substrates and glass substrates are widely used as substrates for magnetic recording medium. Aluminum substrates consist of a mirror-polished base made of an Al—Mg alloy on which an alloy film consisting of a Ni—P type is formed by electroless plating, the alloy film being about 10 μm in thickness, and the surface thereof being further mirror-finished. Glass substrates are of two kinds, an amorphous glass and glass-ceramics. Glass substrates of each kind are mirror-finished.
In the hard disk drive for the magnetic recording medium now commonly used, a non-magnetic primary layer (an alloy of a Ni—Al type, Cr, an alloy of a Cr type or the like), a non-magnetic intermediate layer (an alloy of a Co—Cr or Co—Cr—Ta type or the like), a magnetic layer (an alloy of a Co—Cr—Pt—Ta or Co—Cr—Pt—B type or the like), and a protective layer (carbon or the like) are deposited in sequence on the glass substrate or the aluminum substrate, and a lubricating film which is composed of a liquid lubricant is formed thereon.
As for a method to efficiently produce the magnetic recording medium with a small diameter, for example, Patent Reference 1 discloses a method in which a plurality of small substrates are attached to a disk carrier and are formed by deposition simultaneously by sputtering, and Patent Reference 2 discloses a method in which a palette is rotated when a plurality of substrates are attached to the palette and are deposited simultaneously.
Patent Reference 1: Japanese Unexamined Patent Application, First Publication No. 2002-280443
Patent Reference 2: Japanese Unexamined Patent Application, First Publication No. 2000-265271
As disclosed in Patent Reference 1, a plurality of substrates are mounted on a substrate holder, and by performing film deposition on these substrates simultaneously, the productivity of a small magnetic recording medium can be enhanced; however, the properties of the produced magnetic recording medium vary with the surface. This is because a disk-like target and a center axis of a plurality of substrates do not align with each other, so that there is a distribution in film thickness deposited on the surface of the substrate. To solve these problems, the method disclosed in Patent Reference 2 rotates the substrate holder during the film deposition, however, the structure of the substrate holder becomes complex. Thus, plasma generated during sputtering becomes unstable, causing the properties of the magnetic film to decrease, and dust from a complex rotating structure causes production yields of the magnetic recording medium to decrease.